1. Field of the Invention
This invention relates to high pressure cryogenic pumps and more particularly relates to a double-acting, reciprocating piston, high pressure (about 2,000 psi and greater) cryogenic fluid pump that provides venting of blow-by vapors between two sets of high pressure seals on a double-acting piston.
2. Background Information
The generation and accumulation of fluid vapors from blow-by leakage in high pressure cryogenic pumps is a significant problem unless the vapors are collected and condensed in cold low pressure liquid. This invention is directed to a method and apparatus for collecting, mixing, and condensing blow-by leakage vapors with cold suction liquid.
One type of double-acting, reciprocating, piston cryogenic fluid pumps is disclosed and described in U.S. Pat. No. 5,411,374 of A. Gram issued May 2, 1995. This patent describes a double-acting, reciprocating piston, cryogenic fluid pump mechanically coupled to a double-acting hydraulic piston motor. The double-acting, reciprocating piston, cryogenic fluid pump shown in the figures and described in the text does not contain any reference to a dual set of piston seals nor does it describe a venting provision relative to the seals. Another U.S. Pat. No. 3,456,595 of C. F. Gottzmann issued Jul. 22, 1969 discloses a double-acting, reciprocating, piston pump for low pressure pumping and metering cryogenic fluids. FIG. 2 of this patent shows a double-action pumping cylinder having venting ports 28 in the working chamber. The venting system disclosed and described herein is to vent-off vapors formed during the suction stroke. The problem of venting “blow-by vapors” is not present in a low pressure pump. Another U.S. Pat. No. 3,181,473 of Duron, the inventor of the invention disclosed herein, issued May 4, 1965 and incorporated herein by reference describes improvements to a single-acting, reciprocating piston, high pressure, cryogenic fluid pump. A design feature disclosed and described in this patent traps and returns blow-by vapors to a cryogenic storage tank.
None of these patents teach or suggest an effective method for venting of blow-by vapors in double-acting pump. It would therefore be advantageous if a method could be conceived to handle this particular problem.
It is therefore one object of the invention to provide a sealing system as well as a venting system for a double-acting, high pressure reciprocating piston pump for pumping cryogenic fluids.
Another object of the present invention is to disclose a double-acting, high pressure reciprocating piston pump for cryogenic fluids that has a significantly reduced peak torque when compared with conventional single-acting pump of similar capacity and pressure rise.
Yet another object of the present invention is to provide a double-acting reciprocating piston pump that has smoother suction and discharge flows and less heat leak into the cryogenic fluid when compared with single-acting, reciprocating piston pump of similar capacity and pressure rise.
Still another object of the present invention is to disclose a double-acting, reciprocating piston, cryogenic fluid pump having a significantly improved suction performance due to the smoother inlet suction flow and less heat leak into the cryogenic fluid when compared with a single-acting, reciprocating piston pump of similar capacity and pressure rise.
Yet another object of the present invention is to disclose a multi-cylinder, double-acting, reciprocating piston, cryogenic fluid pump with improved venting of blow-by vapors.